package algorithm.poj.p1000;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLDecoder;
import java.text.DecimalFormat;
import java.util.Arrays;

/**
 * 分析：
 * 
 * 
 * 实现：
 * 
 * 经验：
 * 需要优化!!!
 * 
 * 教训：
 * 
 * @author wong.tong@gmail.com
 *
 */
public class P1862 {

	@SuppressWarnings("unchecked")
	public static void main(String[] args) throws Exception {

		InputStream input = null;
		if (false) {
			input = System.in;
		} else {
			URL url = P1862.class.getResource("P1862.txt");
			File file = new File(URLDecoder.decode(url.getPath(), "UTF-8"));
			input = new FileInputStream(file);
		}
		
		BufferedReader stdin = new BufferedReader(new InputStreamReader(input));

		String line = stdin.readLine();
		int N = Integer.valueOf(line);
		double[] a = new double[N];
		for (int i = 0; i < N; i ++) {
			line = stdin.readLine();
			a[i] = Double.valueOf(line);
		}
		for (int i = 0; i < N-1; i ++) {
			double[] b = new double[a.length-1];
			Arrays.sort(a);
			for (int j = 0; j < b.length-1; j ++) {
				b[j] = a[j];
			}
			b[b.length-1] = 2*Math.sqrt(a[a.length-2]*a[a.length-1]);
			a = b;
		}
		System.out.println(new DecimalFormat("##0.000").format(a[0]));
	}
}